anisotropic refinement with regard to global coordinate direction

[Simon]

Dear all,

attached is a minimal example in which I create two simple triangulations (tria1, tria2),

merge them, and finally anisotropically refine all cells (RefinementCase<3>::cut_xz).

I also write the merged triangulation to a file for visualizations sake.

My objective is to refine only in the global xy plane, that is, in global z-direction, I want to have one element everywhere (if hanging nodes allow that, of course).

For the given example,

RefinementCase<3>::cut_xz

is correct for tria1, but not for tria2.

I read the documenation which states that anisotropic refinement occurs w.r.t the local coordinate system of the cell, so I am not really surprised about the above result.

Anyway, is there a way to perform anisotropic with regard to the global system?

My ideas was to, based on the local orientation of the cell system, pass a different RefinementCase when marking the cells for refinement.

The TriaAccessor class offers the combined_face_orientation() function, but I am

not sure if it helps here.

Thank you for your input!

Best,

Simon